The HOV lane is also known as the carpool lane. HOV stands for “high occupancy vehicles.” This usually means that they are carrying two or more people.
The basic idea behind these lanes is to have more people and less cars, causing a reduction in overall traffic. The California DMV notes that, “Each child counts as an occupant, but pets, infants still in the womb, inflatable dolls or ghosts do not (we've heard 'em all).”
The bus-only lane on Shirley Highway (I-395) in Northern Virginia outside Washington, D.C., in 1969 is considered the first freeway HOV application in the United States.
On a side note, Nicki Manaj has released a new song titled “HOV Lane.”